1. Field of the Invention
The invention involves a flow through cell that is a photometric detector for determining the chemical composition contents in fluid. Especially, it is used for photometric detection in the flowing station, which belongs to the chemical analysis instrument.
2. Background of Related Art
The flowing spetrophotomatic analysis is a channelization continuous flow analysis; the sample is injected into the carrier solution and reacts with the carrier solution or the reagent in the carrier solution. Subsequently, the sample flows into the detector with constant speed along the carrier solution. This method is simple, quickly analysis speeds, high precision, easy automation continuous analysis. Recently, it has shown a wide application in variety fields such as environments, clinic, medicines, agroforestry, metallurgical geology, industrial process monitoring, biochemistry, food; Furthermore, the photometric colorimeter with the flowthrough cell is used the most one of the photometric detectors in FIA.
The base of the cell is furnished with a fluid inlet and wastewater outlet, and there is a fluid pathway inside the base that connects with the above inlet and outlet. The fluid pathway includes two turns at least. The optical path locates between the optical entrance and optical exit, and its both ends locate in the turning position of the fluid pathway. According to the shape of fluid pathway, the traditional flowthrough is classified into Z-type (see FIG. 1), H-type (see FIG. 2) and U-type, etc. Regardless of the type, both ends of the optical pathway must have a quartz glass window or a glass window, while the fluid pathway is directly graved inside the base. When the fluid transporting tube connects with the base inlet, the fluid would flow out form the outlet along the base groove rail under the pump propelling and flow through the optical pathway. The fluid irradiated with light to detect in photometric analysis. The disadvantages of the current flowthrough cell are: {circle around (1)} the diameter of the flow transporting tube and optical path is inconsistent and there is a dead angle between the both ends of optical path which results in the state of fluid changing form original stable laminar to turbulent, furthermore which could produce refraction of light and display interference peak; If the interference peak affects the results seriously that will destroy the peak value to produce the measurement error; {circle around (2)} because of the poor smooth finish inner wall of the pathway, the micro-bubble in water could be detained and adsorbed on the pathway, which the micro-bubble is not to be discharged that could cause light scattering and false absorption to bring measurement error; {circle around (3)} the glass window and quartz glass window occur the leakage easily under high pressure; Or because of the temperature changing, the expansion coefficient of material is different which could also cause the leakage; {circle around (4)} the flow pathway utilizes multi-produce such as furrow, polish, etc. SO, that is complicated technology, very high precision requirement, high production cost and has difficult in meet the accuracy requirement. Presently, the method has never been found to solve the above defects of traditional flow pathway. Especially, the limitation is distinct when the flowthrough cell is used to detect the strong corrosive and strong oxidative fluid.